A coordinated series of histochemical, quantitative morphometric, connectional neuroanatomical, Golgi, and immunocytochemical experiments are proposed to study the intrinsic organization of the pontine taste area (PTA) in the adult hamster. Special emphasis is placed on the positive identification and overall appearance of the PTA, characterization of its morphological distinct classes of neurons and the patterns of terminations of afferent input arising from the gustatory zone of the nucleus of the solitary tract (NST). Parallel studies are carried out at the light and electron microscopic levels. Ongoing work in the gustatory NST serves as the benchmark for these new studies of the PTA. Once the PTA is precisely localized, the classes of neurons within the PTA are categorized and defined using quantitative morphometric procedures and electron microscopy. The efferent projections of the PTA are also studied with the use of the anterograde transport of tritiated amino acids and autoradiography; output neurons are identified by the retrograde transport of fluorescent markers and horseradish peroxidase injections into major efferent targets of the PTA. Light and electronmicroscopic immunocytochemical studies associate classes of neurons in the PTA with putative neurotransmitters or neuromodulators. This proposal represents a long term research plan that extends our analysis of the gustatory brainstem nuclei to the next rostral relay station in the processing of gustatory information and continues our efforts to clarify the basic anatomical principles governing the processing of gustatory information.